Amino(meth)acrylate polymer or copolymers are well known to be used for instance as coating or binding agents in the field of Pharmacy (U.S. Pat. No. 4,705,695). Amino(meth)acrylate polymer or copolymers can be for instance composed of polymerized units of 30 to 80% by weight of C1- to C4-alkyl esters of acrylic or of methacrylic acid and 70 to 20% by weight of alkyl(meth)acrylate monomers having a tertiary amino group in the alkyl radical. EUDRAGIT® E and EUDRAGIT® EPO are examples for these kind of polymer or copolymers and composed of polymerized units of 25% by weight of methyl methacrylate, 25% by weight of butyl methacrylate and 50% by weight of dimethylaminoethyl methacrylate.
These kind of polymers are soluble in organic solvents but insoluble in pure or demineralised water. Amino(meth)acrylate polymers or copolymers are soluble in aqueous buffered media below pH 5.0 but insoluble at higher pH values. Thus Amino(meth)acrylate polymer or copolymers are often used for the coating of pharmaceutical compositions to realize a taste masking effect in the mouth combined with a rapid active ingredient release in the stomach. Amino(meth)acrylate polymer or copolymers may also show positive effects on the storage stability of pharmaceutical compositions due to prevention of moisture uptake.
The coating with amino(meth)acrylate polymers or copolymers can be easily applied from organic solutions by spray applications. However organic solutions are nowadays more and more avoided due to general environmental and health considerations. Therefore aqueous dispersions of coating solutions are usually preferred over organic solutions.
In the case of amino(meth)acrylate polymers or copolymers stable aqueous dispersions can be produced by partially neutralization of the aminogroups in the polymer or copolymers by the addition of acids (U.S. Pat. No. 4,705,695). However the addition of pure acids like HCl for instance may deminish the taste masking ability or the positive effects on the storage stability. Sometimes the use in powder forms and the addition of certain emulgators or fatty organic acids or alcohols may help to overcome these problems.
WO02067906A1 (U.S.20030064036A1) for instance describes a coating and binding agent with improved storage stability, consisting essentially of                (a) a polymer or copolymer, consisting of radically polymerized C1- to C4-alkyl esters of acrylic or methacrylic acid and other alkyl(meth)acrylate monomers which comprise functional tertiary amino groups, the polymer or copolymer being in the form of a powder with an average particle size of 1-40 μm,        (b) 3-15 wt. %, based on (a), of an emulsifier with a HLB value of at least 14,        (c) 5-50 wt. %, based on (a), of a C12-C18-monocarboxylic acid or a C12-C18-hydroxyl compound.        
One of the beneficial effects of the invention is effective taste masking and that the vapour permeability is reduced. Dispersion processing times of the inventive examples are around 3 to 6 hours. However sometimes the use of the amino(meth)acrylate polymer or copolymers in powder form may cause problems with dust. There is also a general trend to avoid the addition at least of larger amounts of excipients.